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foam insulation and roof shingles?

16 years ago

For those of you who have used foam insulation under your rafters, which brand of shingles did you use?

I'm finding that the major manufacturers void their warranties if foam is used without a 1 inch air space between roof decking and foam! How do you get that in an unvented attic?

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Comments (7)

doctj
16 years ago
One of our local companies recommends Elk shingles for spray foam insulated attics. Does add to the cost however.
klabio
16 years ago
Certainteed allows unvented attics if you follow certain parameters. It's spelled out in their warranty on page 5 & 6.

http://www.certainteed.com/NR/rdonlyres/4C2353BB-E4C6-4428-9C6F-9E9E82DFFDFE/0/2008GeneralAsphaltWarranty.pdf
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Hi, I think that the approach of spraying foam under the roof rafters, and making the attic space part of the conditioned space of the house is a good one if done carefully. Seems like it would be a time consuming job to block all the current attic ventilation carefully. If you use closed cell foam, I don't see why there would be any moisture or condensation problem with the roof sheathing. Some of the people who make roof shingles don't like insulation right under the sheathing because it makes the sheathing and shingles run hotter and may reduce their life -- some people think this is bunk. If you have ducts or AC equipment in the attic, moving the insulation line up to the roof rafters will make your AC and duct system more efficient. The FSEC has some papers on what kind of saving results from this. Have you thought about just blowing additional cellulose insulation on the attic floor? Seems like this would be a lot cheaper, and may accomplish about the same result? http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/97/970504.html Gary
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"This method would keep the attic ventilated but cuts back on the radiant heat coming in from the underside of the roof sheathing". If you can use a straight edge, utility knife, and stapler, you can diy this for big savings using rolls of radiant barrier. The install is on the underside of the rafters using the rafter cavaties as channels to trap the heat gain and is pushed out by way of the soffit venting up and out the ridge venting. Here's a link to an outfit that offers different install methods and radiant types. I've used 50" wide x 1000" rolls one side foil faced. fiberglass mesh inbetween, with the opposing side kraft paper. You hold it up 3" from where the rafters meets the top plates and run it perpindicular to the rafters overlapping and foil taping the seams. You overlap at the ridge as well. Your soffit/ridge venting must be continous run meaning every rafter cavaty would be vented to allow the heated air to escape. The radiant blocks it from entering the attic. Very effective anvenue of keeping the attic cool. Here is a link that might be useful: radiant barrier
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txgal06
16 years ago
We used Elk. No air gap. Don't know if the warranty has any changes since they merged with GAF.
carterinms
16 years ago
We used Owens Corning, so have voided the warranty. If our roof fails, it will most likely be during a hurricane, which would (a) be covered by insurance, and (b) be covered by the warranty for only 10 years even if we did have the air gap.
emilynewhome
Original Author
16 years ago
Thanks, that's the same conclusion DH and I have arrived at! The shingle manufacturers warranties have so many exceptions as to what, when and how much they'll pay that the warranty doesn't seem to be worth anything, irregardless of vented or unvented attic!
timwalker69
16 years ago
Gaf bought Elk. Elk was ok with spray foam, GAF was not. The response I got form the regional office in Dallas was that if it could be proven that the shingles suffered a failure due to excessive heat buildup from not having air circulate, then the warranty would be voided. But you are right, most warrantes are not worth the paper written on as there can be so many outs. For instance our 25 yr warranty on carpet. it covers pet stains if absorbed immediately. well we didn't see a few until they had dried. Me being honest said it was dried. Too bad, warranty voided.

I don't beleive spray foam will cause shingle failure. A traditional "vented" attic here in Houston approaches 135-140F in the summer. So the shingles see that from the underneath side also. However, builders here with totally unvented attics are seeing temps in the uper 80's to lower 90's in mid summer. Umm. Do the math.

Tim in houston
msm859
16 years ago
I have a tile roof with foam insulation - unvented attic. Do not know about warranty however, my attic runs a lot cooler than the "vented" attics. So I don't know how they can "successfully" claim it voids any warranty. As an attorney I would take them to court over that claim.

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